The air to fuel (A/F) ratio in a combustion engine affects both engine emissions and performance. With current emissions standards for automobiles, it is necessary to accurately control the A/F ratio of the engine. Accurate control requires precise measurement and/or estimation of the mass air flow into the engine.
Traditionally, engine air flow is measured with a mass air flow (MAF) sensor or calculated using a speed-density method. While MAF sensors are more accurate than speed-density calculation systems, they are also more expensive. An estimation-prediction method dynamically determines air flow into the engine using a mathematical model. While this method enables more precise A/F ratio control than traditional methods, inaccuracies may occur as a result of calibration difficulties.